Exploring The Universe

A Quasar in the Gamma-Ray Sky - November 17th, 1996.

"The bright object in the center of the false colour image above is quasar 3C279 viewed in gamma-rays, photons with more than 40 million times the energy of visible light. Like all quasars, 3C279 is a nondescript, faint, star-like object in the visible sky. Yet, in June of 1991, a gamma-ray telescope onboard NASA's orbiting Compton Gamma Ray Observatory unexpectedly discovered that it was one of the brightest objects in the gamma-ray sky. Shortly after this image was recorded, the quasar faded from view at gamma-ray energies. Astronomers are still trying to understand what causes these enigmatic objects to flare so violently. Another quasar, 3C273, is faintly visible above and to the right of the center."

The Leonid Meteor Shower '(Tonight)' - November 16th, 1996.

"On November 16th, 1996, thousands of icy rocks would hurl toward Earth in a fascinating display called the Leonid meteor shower. There was little danger - few of them would reach the ground. Meteor showers result from debris left by passing comets. The Leonids in particular are small pieces of Comet Tempel-Tuttle. In the above series of time-lapse, 1-minute exposures, a 1995 Leonid is seen to leave a train of hot air that glowed persistently for several minutes."

Searching For Solar Systems - November 15th, 1996.

"Observational astronomy has provided evidence of the existence of massive Jupiter-sized planets orbiting distant suns, protoplanetary disks of gas and dust surrounding newly formed stars, and planetary bodies orbiting exotic stellar corpses known as pulsars. Indeed, the formation of planets seems to be a broader and more varied phenomenon than previously imagined. Are there nearby solar systems with Earth-sized planets as well? Many would answer yes, but small, relatively low mass planets orbiting sun-like stars - which might be capable of supporting life - are extremely difficult to detect. One possible approach to this daunting observational problem is to regularly monitor the light from many solar-type stars, searching for the slight decrease in brightness which signals the transit of a small planet in front of the stellar disk. A proposal for a space-based instrument to engage in such a program, the Kepler Mission, is illustrated above. In this concept, the monitoring space telescope orbits the Sun, slowly drifting away from Earth. The goal of this mission would be to discover Earth-sized planets in the habitable zone of solar-type stars, taking a step toward answering the profound question - Does life exist on other worlds beyond our Solar System?"

Supernova Remnant and Neutron Star - November 14th, 1996.

"A massive star ends life as a supernova, blasting its outer layers back to interstellar space. The spectacular death explosion is initiated by the collapse of what has become an impossibly dense stellar core. However, this core is not necessarily destroyed. Instead, it may be transformed into an exotic object with the density of an atomic nucleus but more total mass than the Sun - a neutron star. Directly viewing a neutron star is difficult because it is small (roughly 10 miles in diameter) and therefore dim, but newly formed in this violent crucible it is intensely hot, glowing in X-rays. Images from the ROSAT X-ray observatory above may offer a premier view of such a recently formed neutron star's X-ray glow. Pictured is the supernova remnant Puppis A, one of the brightest sources in the X-ray sky, with shocked gas clouds still expanding and radiating X-rays. In the inset close-up view, a faint pinpoint source of X-rays is visible, which is most likely the young neutron star, kicked out by the asymmetric explosion and moving away from the site of the original supernova at about 600 miles per second."

Seven Jets from Comet Hale-Bopp - November 13th, 1996.

"Comet Hale-Bopp turned out to be quite unusual. One reason was the great amount of jet activity at such a large distance from the Sun. In the above false-colour image, no less than seven jets can be seen emanating from Hale-Bopp's coma. As the comet neared the Sun, its surface warmed, causing jets of previously trapped gas and dust to stream away from the nucleus. Astronomers continued to study Comet Hale-Bopp's unusual jet activity and wondered how much about the early Solar System Hale-Bopp would teach them, and how bright Hale-Bopp would ultimately become."

Comet Hale-Bopp Passes M14 - November 12th, 1996.

"Comet Hale-Bopp continued its slow trek across the night sky, and could be seen superposed near the bright globular cluster M14. Hale-Bopp was holding at about 5th magnitude - just barely bright enough to see without binoculars from a dark location. Because of the size of the coma, some speculated that the nucleus of Hale-Bopp was unusually large. The actual nucleus is obscured, however, and more speculation included that the nucleus was comparable in size to Comet Halley - about 10-15 km across."

NGC 4755: A Jewel Box of Stars - November 11th, 1996.

"The great variety of star colours in this open cluster underlie its name: The Jewel Box. The bright central star Kappa Crucis is red, in contrast to the many blue stars that surround it. The cluster contains just over 100 stars, and might be no older than 10 million years. Open clusters are younger, contain few stars, and contain a much higher fraction of blue stars than globular clusters do. This Jewel Box lies about 7500 light-years away, so the light that we see today was emitted from the clusters before even the Great Pyramids in Egypt were built."

Columbia Launches - November 10th, 1996.

"Rocket engines blazing, the Space Shuttle Columbia arcs into Florida's morning sky after lifting off from pad 39-A at Kennedy Space Center. Seen here in January of 1996, this space shuttle had, at that time, been operational for more than 15 years - racking up 20 flights and over 77 million miles in orbit while spending 177 days in space. The first member of NASA's shuttle fleet, Columbia shares its name with another famous spacecraft launched from pad 39-A, the Apollo 11 command module."

Surveyor Hops - November 9th, 1996.

"This panorama of the cratered lunar surface was constructed from images returned by the US Surveyor 6 lander. Surveyor 6 was not the first spacecraft to accomplish a soft landing on the Moon, but it was the first to land and then lift off again! After touching down near the center of the Moon's nearside in November of 1967, NASA controllers commanded the spacecraft to hop. Briefly firing its rocket engine and lifting itself some 4 meters above the surface, the Surveyor moved about 2.5 meters to one side before setting down again. The hopping success of Surveyor 6 essentially marked the completion of the Surveyor series' main mission - to determine if the lunar terrain was safe for the planned Apollo landings."

A Solar Corona Ejection - November 8th, 1996.

"The Sun would not be a nice place to spend the summer. One reason, besides the extreme heat, is that explosions are common there. In the above picture, magnetic fields buckle, releasing previously constrained hot material from the upper atmosphere of the Sun. As a result, hot gas streams out into the Solar System, impacting planets, moons, spacecraft, and making space a dangerous place for astronauts. Known as coronal mass ejections (CMEs), billions of tons of scathing plasma can be accelerated to millions of miles per hour. CMEs are more common but less intense than solar flares."

Fields of Minerals on Ganymede - November 7th, 1996.

"What treasures lie on the surface of Ganymede? NASA had released a map of Jupiter's largest moon, made by the Galileo Orbiter, highlighting ice and mineral deposits. The leftmost photograph by Voyager shows surface features in visible light, but the rightmost photograph, taken in infrared light by Galileo, shows the locations of minerals in red and ice grains in blue."

Elliptical Galaxy NGC 4881 in Coma - November 6th, 1996.

"Elliptical galaxies are unlike spiral galaxies and hence unlike our own Milky Way galaxy. The giant elliptical galaxy named NGC 4881 on the upper left lies at the edge of the giant Coma Cluster of Galaxies. Elliptical galaxies are ellipsoidal in shape, contain no spiral arms, contain little interstellar gas or dust, and are found mostly in rich clusters of galaxies. Elliptical galaxies appear typically yellow-red, as opposed to spirals which have spiral arms that appear quite blue. Much speculation continues on how each type of galaxy can form, on whether ellipticals can evolve from colliding spirals, or spirals can be created from colliding ellipticals, or both. Besides the spiral galaxy on the right, all other images in this picture are of galaxies that lie well behind the Coma Cluster."

The Coma Cluster of Galaxies - November 5th, 1996.

"Almost every object in the above photograph is a galaxy. The Coma Cluster of galaxies pictured is one of the densest clusters known - it contains thousands of galaxies. Each of these galaxies house billions of stars - just like our own Milky Way galaxy. Although nearby when compared to most other clusters, light from the Coma Cluster still takes hundreds of millions of years to reach us. In fact, the Coma Cluster is so big it takes light millions of years just to go from one side to the other! Most galaxies in Coma and other clusters are ellipticals, while most galaxies outside of clusters are spirals."

The Martian Spring - November 4th, 1996.

"As spring comes to the northern latitudes of Mars, increased solar heating brings warmth and a change in the weather. The winds produced by the large temperature differences between the receding polar ice and the warming regions to the south may cause dust storms - like the one visible in the above Hubble Space Telescope image made in September, 1996. On the left, north is up and the Martian polar cap is seen at the top with dark regions along its southern border. The dust storm, about 600 miles wide, is visible against the white polar ice as a salmon coloured notch. The image on the right presents the data showing the dust storm on a map grid centered on the north pole. Mars is famous for planet wide dust storms but studies of more localised weather patterns are difficult without high resolution images like those provided by Hubble. As NASA prepares future missions to Mars, detailed studies of Martian weather patterns become increasingly important."

Surveyor Night Launch - November 3rd, 1996.

"In early November of 1967, a dramatic night launch of an Atlas Centaur rocket from Cape Canaveral lofted the successful Surveyor 6 spacecraft toward the Moon. The Surveyor series of robotic probes carried out the first US lunar soft landings in preparation for the Apollo program. Atlas Centaur rockets launched many lunar and planetary probes in the 60s and 70s."

Spiral Galaxy NGC 253 Almost Sideways - November 2nd, 1996.

"NGC 253 is a normal spiral galaxy seen here almost sideways. It is the largest member of the Sculptor Group of galaxies, the nearest group to our own Local Group of galaxies. NGC 253 appears visually as one of the brightest spirals in the sky, and is easily visible in the southern hemisphere with a good pair of binoculars. This type of "Sc" galaxy is about 10 million light years distant. NGC 253 is considered a "starburst" galaxy because of high star formation rates and dense dust clouds in its nucleus. The energetic nuclear region is seen to glow in X-ray and gamma-ray light."

Spiral Galaxy NGC 3628 Edge On - November 1st, 1996.

"This is what a spiral galaxy looks like sideways. This view of NGC 3628 resembles our own Milky Way galaxy, which is also known to be a spiral. The dark band across the center is absorbed starlight caused by the galaxy's interstellar dust. NGC 3628 is the faintest member of the Leo Triplet, a group of galaxies dominated by M65 and M66. The Leo Triplet lies about 35 million light years distant. The center of NGC 3628 emits variable X-ray radiation, perhaps indicating the presence of a massive black hole."